1. Field of the Invention
The present invention relates to a cooling water circulation apparatus and a method of removing scale from a cooling water circulation apparatus.
2. Description of Related Art
A cooling water circulation apparatus for circulating cooling water in a water-cooled appliance or the like, e.g., one disclosed in Japanese Patent Laid-Open No. 2000-140858 is known. In this apparatus, a heat exchanger or the like of the appliance is cooled by cooling water, and the cooling water thereby made warm is returned to a cooling tower to be cooled and is again circulated to the heat exchanger.
In such a cooling water circulation apparatus, water insoluble calcium salts (scale) may deposit on an inner wall of piping, or algae or microorganisms may multiply to cause a clogging in the piping or reduce the cooling efficiency. Multiplication of microorganisms in the apparatus is also undesirable in terms of hygiene. Therefore it is a common practice to add chemicals such as a sterilizer and-an antiscalant to cooling water. If the hardness of cooling water is increased by evaporation of water with elapse of time, deposition of scale occurs easily. A method of monitoring the hardness of cooling water at all times and changing the cooling water in a cooling tower when the hardness becomes equal to or higher than a prescribed value has also been practiced.
In recent years, however, self-control on use of chemicals has been performed from the viewpoint of prevention of environmental pollution. There is a demand for development of a sterilization and scale-deposition prevention method substitutable for use of chemicals.
The method of changing cooling water when the hardness becomes equal to or higher than a prescribed value requires throwing away the entire cooling water in the cooling tower every time it is changed and therefore entails the water resource wasting problem.